1. Field of the Invention
The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device, wherein a touch panel is embedded in a liquid crystal panel, contributing to a reduction in the number of processes and easy assembling.
2. Discussion of the Related Art
As society becomes increasingly information dependent, a display field, wherein electrical information signals are visually displayed, is being developed rapidly. As such, a variety of flat panel display devices having outstanding performances, such as a thin thickness, light weight and low consumption of electricity, have been developed and have rapidly replaced conventional Cathode Ray Tubes (CRTs).
Examples of flat panel display devices include, for example, Liquid Crystal Display (LCD), Plasma Panel Display (PDP), Field Emission Display (FED) and Electro-Luminescence Display (ELD) devices, etc. These devices commonly include, as an essential element, a flat display panel to form an image. The flat display panel is configured such that a pair of transparent insulating substrates is bonded to face each other with an inherent illuminating or polarizing material layer interposed therebetween.
Of the above-mentioned display devices, an LCD device is designed to display an image by adjusting light transmissivity of liquid crystals using an electric field. For this, the LCD device includes a display panel having liquid crystal cells, a backlight unit to irradiate light to the display panel, and drive circuits to drive the liquid crystal cells.
The display panel is provided with a plurality of gate lines and a plurality of data lines, which intersect each other to define a plurality of unit pixel regions. In this case, each pixel region consists of a thin-film transistor array substrate and color filter array substrate opposite each other, spacers located between the two substrates to maintain a cell gap, and liquid crystals filled in the cell gap.
The thin-film transistor array substrate includes the gate lines and data lines, thin-film transistors as switching devices formed at intersections of the gate lines and data lines, pixel electrodes arranged per liquid crystal cell and connected to the thin-film transistors, and an alignment film coated over all the above elements. Signals from the drive circuits are supplied to the gate lines and data lines through respective pads.
The thin-film transistors supply pixel voltage signals, to the pixel electrodes, in response to signals supplied to the data lines and in response to scan signals supplied to the gate lines.
The color filter array substrate includes color filters arranged per liquid crystal cell, a black matrix for division of the color filters and refraction of outside light, a common electrode to commonly supply a reference voltage to the liquid crystal cells, and an alignment film coated over all the above elements.
After the thin-film transistor substrate and color filter array substrate, which are fabricated separately, are aligned, the thin-film transistor substrate and color filter array substrate are bonded to face each other, and liquid crystals are injected and sealed, to thereby complete the display panel.
The demand for the addition of a touch panel to the LCD device fabricated as described above is increasing. A touch panel is designed to sense a touch position of person's hand or other input means and transmit information in response to the sensed touch position. Currently, such a touch panel has been attached to an outer surface of the LCD device.
Hereinafter, a conventional touch panel attached LCD device will be described with reference to the accompanying drawing.
FIG. 1 is a schematic view illustrating a conventional touch panel attached LCD device.
As shown in FIG. 1, the conventional touch panel attached LCD device includes a liquid crystal panel 10 which consists of first and second substrates 1 and 2 respectively, a liquid crystal layer 3 filled between the substrates 1 and 2 and first and second polarizers 4a and 4b, respectively, attached to rear surfaces of the first and second substrates 1 and 2, a touch panel 20 which is placed on the liquid crystal panel 10 and is driven in a capacitive manner, and a cover glass 30 to protect the top of the touch panel 20.
Provided on the first substrate 1 of the liquid crystal panel 10 is a Thin-Film-Transistor (TFT) array consisting of gate lines and data lines intersecting each other to define pixel regions, TFTs formed at intersections of the gate lines and data lines, and pixel electrodes in the respective pixel regions (not shown).
Provided on the second substrate 2 is a color filter array consisting of a black matrix layer, a color filter layer and a common electrode.
The interior configuration of the touch panel 20 is changed according to a driving manner of the touch panel. For example, in the case of a capacitive touch panel designed to sense a touch position via a capacitance variation at a touch point, first and second electrodes intersecting each other are provided to enable sensing via a capacitance value variation between the electrodes.
To protect the touch panel 20, the cover glass 30 is provided on the top of the touch panel 20.
The above-described conventional touch panel attached LCD device requires an adhesive layer (not shown) between the touch panel 20 and the liquid crystal panel 10 because the touch panel 20 is formed as a sheath of the liquid crystal panel 10. In this case, the liquid crystal panel 10 and touch panel 20 must be fabricated separately, and there is a need for a process for attaching the touch panel 20 and the liquid crystal panel 10 to each other.
Problems of the above-described conventional touch panel attached LCD device will be described.
The touch panel is provided as a sheath of the liquid crystal panel and therefore, an adhesive layer must be provided between the touch panel and the liquid crystal panel. This inevitably requires an additional attachment process. Further, if the touch panel and liquid crystal panel are misaligned, it is difficult to separate the touch panel attached to the liquid crystal panel, and forcible separation may damage the touch panel.
In addition, the attachment of the adhesive layer between the touch panel and the liquid crystal panel has a risk of increasing process time and costs due to an increased number of processes.
With the configuration of the touch panel being attached to the liquid crystal panel, the entire LCD device has a total thickness of at least the touch panel, liquid crystal panel, a module surrounding the liquid crystal panel, and a cover glass. Assuming that such a touch panel attached LCD device is used in small devices such as cellular phones, the thick thickness of the entire LCD device becomes a burden.